Thanks from the UK for the really useful information on this forum.

I recently acquired an 04 YZ450F supermoto for riding in speed (strictly tarmac) hill climbs here in the UK (I don't think you have anything like it in the USA). It's way to fast for me at an easy 89 mph through the finish speed trap at a recent event with higher gearing stil posssible. Dyno tested at 60 bhp it is a bit different to my YZ250 stroker.

My son, however, will make proper use of it next year when he is 16 all being well. He is set to come second in the NHCA 250 championship this year on the YZ125 i rebuilt for him and supermoto'd last winter.

Here's the 450:

The stuff on 5 speed conversion was particularly useful as with only the 4 speed box gearing has to be super accurate (I have 3 front and 10 rear sprockets for it) and still it rends to run out of gears to soon on the fast courses. I'll be looking in to getting it done.

I love thumpers, having hill climbed a 510 Husky and a tuned 600 Gilera Nordwest back when I was young enough to keep them wide open.

Thanks again.

what was done to it to get 60HP?

what was done to it to get 60HP?

Dyno optimism would be the first suspect. A genuine 60 hp from a 450 cc YZ450 5 valve is EXTREMELY difficult to achieve. It took Ron Hamp years to get there. What was done on Hamp's flat track engines? Everything, including a custom designed piston crown.

I don't really know what exactly has been done other than it was tuned by "Will Power" here in the UK. The timing cover is engraved "Will Power".

It has one of their manual cam chain tensioners. Probably some dyno optimism. I've got the print out I was given with it in the shed so I might dig it out and post a scan It was prepared for a serious supermoto contender who didn't use it much. I bought it off a racing tyre specialist dealer who got it with a view to building a single cylinder circuit racer using the motor but after trying it out at Mallory Park on tall gearing decided the 4 speed box was unsuitable.

It certainly seems more peppy than my tuned big bore 604cc Nordwest which I had dyno'd at 55 (but a different dyno), but then it's a lot lighter than that was.

OK, so only 58.9 on the best run. Looking at it again reminds me I need to reset the rpm on my gearing calculator spreadsheet. Lots of lovely torque from 6500 to 8500 though.


Ah then there's the SAE v. DIN BHP to consider. My test will have been DIN.

"There are two differences between DIN and SAE horsepower. The first difference concerns the basic units, with which the data are measured. One SAE HP is the force required to lift 550 pounds one foot for one second, or 33,000 pounds per foot per minute. A (metric) DIN HP however, is the force required to lift 75 kilograms one meter for one second. In application of identical power, the SAE HP is therefore 98.629% of the DIN HP. The comparative formula is 100 SAE HP = 101.42 DIN HP = 74.6 kW."

So more like 58 on a US dyno perhaps. Does that sound more achievable?

still impressive.Its showing the bike signing off at 9000 rpm,thought these bikes kept going till 12000 or 12500 and no build up of hp in the low rpm range showing 57 hp at 4000 rpm?

Edited by etuke

57-58, even 59 is believable, but still would require all kinds of work to get there. Ports, oversized carb, modified ignition curve, and of course, cams, lots of work with the cams and timing.

still impressive.Its showing the bike signing off at 9000 rpm,thought these bikes kept going till 12000 or 12500 and no build up of hp in the low rpm range showing 57 hp at 4000 rpm?

I think you are looking at the torque curve. 37 ft-lbs at 4000, 30 BHP and I see the axes actually say 'SAE'. The revs do seem a bit lowe at tthe top end. Perhaps it's not the dyno graph for this bike at all but a CCM 630 (604cc) as the graph ine titles say 630 not 450 :rolleyes:

I'm guessing at least the full WillPower tune up kit which includes cams, chain adjuster and flywheel. To put it in context here are the 64 ft times and finish speed trap results for the 500 class at the same event. The 450 is down as both number 540 and 548. I 'double rode' it with an old friend who is a much better rider than me so I'm not going to show the times for the complete run! The finish is at the end of a decently long straight after a fairly tight hairpin. So the YZ is right up there with some of the quickest 500s. The fastest 1300 class machines (TL1000, Aprilia 1000) clock 110 or so. You can see how the tall first gear is costing tenths off the line. That's why I'm looking at a 5 speed conversion.

Number Bike cc 64ft Speed 10 Honda CRF 470 1.94 91.8 504 Aprilia SXV 450 2.36 88.7 505 Husaberg 470 2.39 87.2 508 Honda CRF 470 2.15 87.7 511 Honda CRF 450 2.04 91.6 531 Yamaha ZRF 450 2.49 87.6 540 Yamaha 450 2.35 88.1 548 Yamaha 450 2.53 89 549 Suzuki GSXR 400 2.38 89.4 561 KTM 450 2.92 74 567 KTM 450 2.12 90.8 583 Suzuki 500 2.39 77.1 591 Aprilia SXV 450 2.06 90.9

Right. Love this forum. 3 months ago I didn't know sh*t and from everyone's help I can do a lot to my bike. Thanks from the states for the EPL. Go Chelsea!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now